Prior art of possible relevance includes my prior U.S. Pat. No. 3,706,307 issued Dec. 19, 1972 and U.S. Pat. No. 4,016,867 issued Apr. 12, 1977 to King et al.
With the increasing awareness of the importance of endometrial cavity size to intrauterine device insertion and performance and of unique anatomical conditions which suggest individualization of medical management, there have evolved a number of proposals of measuring instruments as, for example, those disclosed in the previously identified United States patents. While such instruments have functioned satisfactorily for their intended purpose, room for improvement exists.
For example, in the instrument described in my prior U.S. Pat. No. 3,706,307, the measuring scale begins in close proximity to the distal end of the probe forming part of the instrument with the consequence that, in some instances, the scale may be wholly or partially obscured by the patient's body making it difficult to read. Furthermore, the stop employed in that instrument, in the form of the sleeve, must be manually positioned against the cervix by the physician using the instrument. Since the stop forms part of the measuring apparatus, if not properly placed, the dimensions of the uterus or cervical canal cannot be accurately determined.
King et al disclose a similar measuring instrument which avoid the forementioned problems. King et al spring bias the stop in the direction of the distal end of the probe such that the spring urges the stop against the cervix eliminating the need for manual placement of the stop by the physician. Furthermore, King et al locate the measuring scale at the proximal end of the probe where the likelihood that it will be obscured by a portion of the patient's body is eliminated entirely. However, in accomplishing these improvements, King et al have introduced a disadvantage in that the biasing spring employed in connection with the stop is a coil spring which is exposed on the probe, which may come in contact with the tissue of the patient during a measuring procedure and which may cause patient discomfort by reason of the collapsing of the convolutions of the coil spring upon one another while the probe is being inserted and after the stop has abutted the cervix.
The present invention is directed to overcoming one or more of the above problems.